1. Field of Invention
The present invention relates to the field of antennas and, more particularly, to channelized log-periodic antennas.
2. Description of the Prior Art
Astronomical observations in spectral regions ranging from approximately the far infrared (far IR) wavelengths to millimeter (mm) wavelengths are opening a new window on the universe. Studies of the Cosmic Microwave Background (CMB) are testing cosmological models, providing more precise values of cosmological parameters, and helping to elucidate the origin of structure in the universe. It is anticipated that our understanding of star and galaxy formation is likely to be revolutionized by observations at far IR and sub-mm wavelengths since much of the light from early stars that is emitted in visible and ultraviolet (UV) wavelength regions is absorbed by dust and re-radiated at these longer wavelengths. The astronomical science in this wavelength regime has been given the highest priority by the astronomical community.
Many wideband planar antennas are described in the literature, but one challenge is to produce an antenna that is capable of measuring two polarizations of radiation simultaneously and that can be coupled to transmission lines that are practically fabricated using, for example, lithography on a silicon substrate. Producing such an antenna is one objective of the present invention.
An antenna that truly has no change in behavior or performance characteristics with frequency has no characteristic length scale and the features are characterized by azimuthal angle. Examples of such antennas include the bowtie and spiral antennas. In the case of the bowtie antenna, the impedance depends on the opening angle of the bowtie. The bowtie is not a resonant antenna. An ideal bowtie antenna should be infinitely long. The length at which it is truncated limits its bandwidth.
Another class of antenna has components with lengths that are related to wavelength, but the antenna can be scaled (stretched) to obtain a periodic structure with a scaling factor. Antennas in this class include log-periodic (LP) antennas. The properties of these antennas (for example, beam pattern, impedance, among others) may change periodically with wavelength, but this periodicity can be reduced or minimized in specific embodiments of a particular antenna design.
Thus, a need exists in the art for an improved broadband antenna, especially in the far-IR to sub-mm wavelength regions, capable of simultaneously detecting at least two polarizations.